It can be understood that some industries such as laser applications are in need of converting light spot position into electrical signals such as a pulse with pulse width determined according to the light spot position sensed thereat.
One typical scheme adopted by conventional art to convert a light spot position into an electrical signal such as a pulse with pulse width determined according to the sensed light spot position, is shown in FIG. 1 where the converter PSD converts a light spot position into two photo currents 1.times.1 and 1.times.2 respectively outputted from its two electrodes and determined according to the distances from the sensed light spot position to its two electrodes. These two photo currents are converted by operational amplifiers (OP AMP) A1 and A2 into voltages which are processed by two arithmetic circuits to provide a divider with two voltages (V.times.2-V.times.1) and (V.times.2+V.times.1). An signal (V.times.2-V.times.1)/(V.times.2+V.times.1) is then outputted by the divider in response to the two voltages, and is inputted to a voltage-to-pulse width converter which is thus able to provide a pulse with pulse width depending on the light spot position. It can be realized a simpler circuit shall be significant to some applications.